Method of making layers sensitive to light



Patented Dec. 3, 1940 UNITED STATES DIETHOD OF MAKING LAYERS SENSITIVE T LIGHT Evert Ragnar Elvezard, Stockholm, Sweden No Drawing. Application March 1c, 1938, Serial No. 196,286. In Sweden February 11, 1938 2 Claims.

Further, it is known, when carrying out this method, to use two baths with substances dissolved in water and to give such concentrations to the solutions that the whole quantity of salt absorbed by the foil from the first bath, the socalled impregnation bath, is decomposed when treating the 011 in the second bath, which serves as a precipitating agent. The heretofore disclosed method of reaching this result is described to be to keep the molar concentration of the precipitating bath equal to or greater than the molar concentration of the first bath. It has been considered that, if the second bath were molarly more diluted than what has been mentioned above, the precipitate would not be located entirely within the foil but would, at least in parts, form also outside the same in the precipitating bath proper; further, the foil would not possess a smooth and homogeneous appearance.

Yet, films produced in this manner have the drawback of being relatively little light-sensitive, so that considerable times of exposure, also in strong light, are required when they are used for photographic purposes.

The present invention relates to a method of producing light-sensitive layers, which possess a greater light-sensitivity and, therefore, are more useful for various photographic purposes.

The invention is characterized by two moments:

(1) The use of at least 3 different solutions;

(2) A certain relation between the concentration of the dissolved substances in these solutions.

By treating the layer with three or more solutions the advantage is obtained that it ispossible to precipitate several different compounds in a certain succession in the layer, which tonormal concentration of a substance in a later used solution must be at least four-tenths of the equivalent-normal concentration of a substance in a previously used solution, with which the first-mentioned substance reacts.-

As an example of the use of the invention may be given the precipitation of silver iodide and silver bromide within a viscose foil. In such a case silver iodide should be precipitated first in the'foil and then silver bromide. It is possible, however, first to precipitate silver bromide and silver iodide together, but such precipitation should be followed by a precipitation of silver bromide only.

Example 1 15 'Bath a: 1.0 N. Kl.-

Bath 1): 0.4 N. AENO: Bath 0: 0.16 N.KBr

Example 2 Bath a: 1.0 N. Kl

Bath b: 0.4 N. AgNOs Bath 0: 1.0 N. AgNO: Bath d: 0.4 N. KBr

Example 3 4 Bath a: 0.1 N. in Bath b: 0.4 N. ASNO:

Bath c: 1o N. KBr $5 limample 4 Bath a: 0.2 N. AgNOa Bath 17: 0.3 N. KI

Bath :2: 0.6 N. AgNOa 40 Bath d: 1.0 N. KBr

If, for example, the first bath contains both KI and KBr and the second bath AgNOa, which thus reacts with both of the salts in the first bath, the sum of the reacting salts in the first solution is to be counted.

' Example 5 Bath a; 0.2 N. KI+0.3 N. KBr

Bath b: 0.2 N. AgNOs Bath 0: 0.5 N. KBr.

Analogous is the case, if a following solution contains several substances that react with the substance in a previous solution.

Example 6 Bath 0: 0.8 N. KI Bath b: 1.0 N. AgNO: Bath 0: 0.3 N. KBr+O.1 N. NaCl.

According to the invention it is of importance that, if silver iodide is formed in the layer, the same, after the formation of silver iodide has taken place, is treated with a substance influencing the light-sensitivity, which does not consist of nor contains iodine. Preferably, the layer, after the silver iodide is formed, is treated with chlorine or bromine or with a compound containing silver, chlorine or bromine.

For example, a viscose foil is first bathed in a solution obtained by dissolving 0.01 mole potassium iodide in one litre of water. After the foil has been thoroughly impregnated with this solution it is moved to a solution consisting of 0.03 mole silver nitrate in one litre of water, in which case the potassium iodide in the foil will react with penetrating silver nitrate, so that insoluble silver iodide is precipitated within the foil. After the foil has been bathed in the solution of silver nitrate for a suitable length of time, itis removed therefrom and is immersed in a third solution, in which 0.5 mole potassium bromide per litre has. been dissolved. Now ions of bromine will penetrate into the foil, where they react with silver nitrate in excess, so that insoluble silver bromide precipitates in the foil. It is left an open question whether this silver bromide is precipitated beside already existing silver iodide or if the former forms mixed crystals or complex compounds with the latter.

' A film produced in this manner possesses a considerable sensitivity to light. If, on the other hand, the foil had been treated, for example,

' first in the solution of potassium bromide, then in the solution of silver nitrate and, finally, in the solution of potassium iodide, a film would have been obtained, the light-sensitivity of which would have been considerably lower.

As examples of other successions than hereinbefore described for bathing the foil in the solutions the following may be mentioned:

Example 7 KBr- AgNOa K[ AgNOc KBr Example 8 m+mr AgNo3- Nac1 The invention is not limited to cellulose foils.

' It may be applied to any colloids, in or on which light-sensitive silver salts are precipitated by successive treatment with solutions of substances suitable therefor. As examples of colloids,

' which thus may be used may be mentioned gelatine, casein, dextrine or albumin. A layer consisting of, for example, gelatine, applied to a base of, for example, glass or Celluloid, may thus be made light-sensitive by treatment in solutions of silver salts and halides or other suitable substances.

But not even a colloid need be used as a binding agent for the precipitated, insoluble silver salts. For example, by adhesion or adsorption, the same may be fixed to a suitable base. Thus, for example, by combining two solutions, containing silver nitrate and sodium chloride, it is possible to obtain a suitable, disperse precipitate treated with solutions of suitable substances, so 5 that other light-sensitive silver salts are precipitated on the same.

The treatment of the layer to be made sensitive to light need not be restricted to bathing in solutions of suitable substances. The solutions may, for example, be rubbed or brushed or be pasted on to the layer.

"It is possible to sensitize the light-sensitive layers produced according to the invention by using methods or substances customary for sensitizing photographic material. Thus, the lightsensitivity may be increased, if the layer is subjected to a treatment in heat or with an alkaline medium, for example, a solution of ammonia or an organic amine. Also, an increase of the sensitivity is obtained if sulphur-containing sensitizers, for example, thiosinamine, are supplied to the layer. Also, treatment with silver nitrate, which often is used when hyper-sensitizing common photographic film, may be used 25 with advantage on light-sensitive layers produced according to the invention.

In a similar manner the layers may be sensitized for other regions of the spectrum than those of the silver salts by optic sensitizing by means of substances customary for this purpose, such as cyanines, phthalelns, and the like.

For the rest, the foils may be subjected to all treatments, which are customary in the production of common photographic film with gelatine emulsion.

Several light-sensitive layers of diiferent characters may be attached to each other, by which a combined layer may be obtained with desired photographic properties. It is possible also to fasten together one or more prepared layers with one or more unprepared layers of the same matelie! or some other transparent material, for example, of acetate-cellulose or nitro-cellulose.

After the treatment in the various baths the layer may be dried either in the air or in a waterabsorbing liquid, for example, a water-soluble alcohol, ether, ketone, or aldehyde. In such a case it is advantageous to use easily volatile liquids, the drying being accelerated thereby. The drying by means of a liquid brings about the advantage that the foils dry in a plane state without buckling, which easily may be the case when der of a suitable degree of hardness, for exam- .65

ple, emery or pumice. The light-sensitive layers produced in accordance with the invention may be used as negative or positive film. It is, however, also possible to fix them to a base of paper or to coat one side of them with a non-transparent, light-re- 70 fleeting coating, by which the layers may be used for producing pictures for observation in light falling direct on the front side thereof in the same manner as common photographic paper. As examples of a suitable coating may be men- 7 tioned common white oil-point or white cellulose lacquer. Yet, the base need not be white but may have any shade, for example, ivory or chamois, which shades sometimes may give an increased artistic eflect to the picture.

On a suitable occasion during their making the foils may, on one or both sides, be provided with a coating, which is impervious to moisture. As an example of such a coating may be mentioned a colourless transparent intro-cellulose lacquer.

The invention may be applied with advantage in combination withthe object of my application, Serial No. 196,287, filed simultaneously herewith.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a method of making a light sensitive layer using cellulose hydrate as suspension agent by treating the layer with substances, which produce at least one light-sensitive silver compound within the layer. the feature that, after the layer has been subjected to such treatment that silver iodide has been iormed, the layer is subjected to a treatment with a solution containing bromide ions but no other halide ions.

2. A method of making a Baht-sensitive layer using cellulose hydrate as suspension agent consisting in at least three successive treatments of the layer with solutions oi substances, silver iodide being formed within the layer before the last treatment, the sum of the equivalent-normal concentrations of substances in a later used solution being more than four-tenths ot the corresponding sum of substances in a previously used solution with which the first mentioned substances react, the last treatment, after the silver iodide is formed, being performed with a solution, containing bromide ions but no other halide ions.

EVERT RAGNAR ELVEGARD. 

